Progress in technology has led to structures wherein there is a body of material in which very close regulation of heat is essential, yet physical sizes and interrelationships with other parts of the application where the structure is used, may limit control capability.
One example of an application of such a structure would be a bimetallic planar member used as a precise temperature sensor, where the physical displacement of the member, as it changes shape in response to temperature, is calibrated with respect to a scale, and thus a close control of the temperature of the member at the point from which the calibrated motion is to depart would be essential.
Another example of such a structure would be a planar integrated semiconductor circuit where the overall temperature variation from the power dissipation from the devices therein must not only be transferred to the ambient within narrow temperature variation limits but across the heat dissipating interface there can be regions of higher heat concentration than others caused by different circuitry performing different power consuming functions than others. Close heat transfer control in this type of application has now become a most serious consideration. Thermoelectric coolers have been used quite extensively to assist in heat transfer in downsized and generally inaccessible structures. As examples: in U.S. Pat. No. 4,631,728 the thermoelectric cooler maintains constant the temperature of a laser diode temperature sensor; in U.S. Pat. No. 4,848,090 a thermoelectric cooler is used to control an integrated circuit temperature variation; and in U.S. Pat. No. 4,253,515 different thermoelectric coolers are used at different areas of a planar integrated circuit for different temperature control and moisture control purposes. In each application of a thermoelectric cooler heretofore in the art, the cooler is regulated by a control that is oriented around a reference temperature. Such an arrangement is limited in sensitivity to the quality and sensitivity of the coupling between sensor and thermoelectric cooler.
As continued downsizing and sensitivity progress advances, a need is developing for greater sensitivity in this type of heat control.